1. Field of the Invention
The present invention relates to a fuel vapor pipe structure of a fuel tank of an automobile, particularly relates to a fuel vapor pipe structure using a resin tube.
2. Description of the Related Art
A fuel tank of an automobile is attached with a cut valve for escaping fuel vapor at inside of a fuel tank to outside and preventing fuel rocked by turning or inclining the automobile from leaking to outside of the fuel tank.
Generally, the cut valve is connected to a check valve for making fuel vapor flow to outside when a fuel vapor pressure is higher than a predetermined value and connected to a canister arranged outside of the fuel tank from the check valve.
In connecting the cut valve and check valve, normally, the cut valve and the check valve are connected by outwardly fitting end portions of a tube made of rubber to respective connection tube portions thereof and fastening an outer periphery of the tube made of rubber by hose straps.
Further, there is disclosed a fuel vapor pipe integrated to inside of a fuel tank of an automobile in JP-A-2003-49976, shown below. The fuel vapor pipe is attached to an inner face of an upper wall of the fuel tank and including two branch tubes which include filters at distal ends thereof, a leadout tube led out to outside of the fuel tank is extended from a joining portion of the branch pipe and the leadout tube is connected to a canister via an outside tube. Further, it is described that a tube formed by a composition of a mixture resin of 6, 6-nylon and 6-nylon is used for the pipes.
According to the pipe structure of the background art using a tube made of rubber, after outwardly fitting the tube made of rubber to the connection tube portion, the tube needs to be connected and fixed by the hose strap and therefore, there poses a problem that operability and handling performance are poor and fabrication cost is also high.
In contrast thereto, the resin tube used in the pipe structure of JP-A-2003-49976 comprises a tube made of a resin and therefore, there is achieved an advantage that the tube is light-weighted, handling performance thereof is excellent and fabrication cost is also inexpensive.
However, although in such a pipe structure, strict dimensional accuracy is requested for the resin tube, actually, the dimension is liable to be dispersed by various dispersions, for example, a dispersion by cutting in molding the resin tube, a dispersion by a press-fitting margin in press-fitting the resin tube to connection tubes of respective valve members, a dispersion by contracting the resin tube by a temperature change after being attached to the fuel tank or evaporation of moisture in the resin tube, a dispersion by swelling the resin tube by adhering fuel vapor and so on. Other than these, there is also brought about a dispersion in a distance between the valves by dispersions in dimensional accuracies of a valve member, a bracket connected to a valve member, or the fuel tank per se.
Further, the resin tube is devoid of flexibility and difficult to be elongated in comparison with the tube made of rubber and therefore, when the resin tube is going to attach to inside of the fuel tank in a state of being previously connected with the cut valve or the check valve, by dispersion in an interval between the cut valve and check valve to be connected, there is brought about a drawback that the valves cannot be connected since a length of the resin tube becomes deficient, even when the valves can be connected, the resin tube is liable to be drawn out, and when conversely, the length becomes excessively long, the resin tube is brought into contact with other part to interfere therewith, or a middle portion of the resin tube is hung down and fuel is liable to be stored at the middle of the tube.